1 Your body's nervous system has many important jobs. It can also be divided into three categories. The central nervous system, or CNS, is made up of the brain and spinal cord. It is the center of your body and the center of control and coordination. The peripheral nervous system, or PNS, includes the nerves that reach the outer parts of your body. Finally, the autonomic nervous system, or ANS, includes the nerves that are near the center part of your body. The ANS is actually a smaller part of the PNS. The ANS controls the automatic processes.2 The brain takes up the top half of the inside of the head. The brain is protected by the skull or cranium. The skull bones have holes to let nerves join the brain. These are the cranial nerves. There are twelve of them, and different ones branch to different places, such as to the head, to the face, to the neck, and to the chest, and to the abdomen. Many blood vessels run through the brain to give it oxygen, water, and dissolved food as well.3 The brain is a grayish, jellylike organ. It is slightly larger than a grapefruit in size. It looks like a huge walnut with many grooves and folds. The brain has many parts.4 The cerebrum makes up 85 to 90% of the brain. The cerebrum holds the centers for sight, sound, taste, smell, and touch. It is the center for thinking, memory, decision-making, and muscle control. The wrinkled part of the cerebrum is the cerebral cortex. It has between 10 and 14 billion neurons! The cerebrum and the cerebral cortex are divided into right and left hemispheres. Each half controls muscles on the opposite side of the body. The left side of the cerebrum controls your ability to read, speak, and do math. The right side of the cerebrum controls your abilities in music, art, and understanding of shape and form.